Yay for posting your first map! I'm new around here too
I like the shape of your coastline and the colors you've used, they're really easy on the eye.
You may want to give the rivers a bit of a workover though ... generally they'll run from high ground (mountains, etc.) to the ocean, and many little streams will feed into them along the way. Yours seem to be doing the opposite; they're splitting on the way downhill.